The invention relates to an on-the-fly calibration mechanism, and more particularly to a circuit, method, and receiver apparatus for performing on-the-fly IQ mismatch compensation (or IRR compensation) when receiver apparatus is operating under a data reception mode.
Generally speaking, a higher-order QAM (Quadrature Amplitude Modulation) communication system may specify a higher signal-to-noise ratio (SNR) requirement. That is, a higher image rejection ratio (IRR) is needed. However, IQ (in-phase and quadrature-phase) mismatches such as gain mismatch or phase mismatch caused by circuit impairments due to manufacturing process, temperature change, or other conditions/factors would inevitably cause IRR degradation.
A conventional solution is to use the same test tone signal to test the analog receiver circuits and then apply digital IRR compensation. Unfortunately, such conventional solution merely compensates fixed IQ mismatches and cannot compensate IQ mismatches caused by temperature change/drift.
Further, other conventional solutions may be provided to alter the circuit structure of analog receiver circuits by doubling the sampling rate or adjusting the phases of IQ mixers as the same phase to compensate IQ mismatches as far as possible. However, these solutions consume more power, and the analog receiver circuits cannot receive symbol signals when the compensation of IQ mismatches is being performed since a local oscillator is needed to be reconfigured and/or the phase difference of IQ mixers is needed to be 90 degrees when the analog receiver circuits receive symbol signals.